1. Field of the Invention
The present invention relates to a pad conditioner, and more particularly to a pad conditioner used for conditioning a polishing pad in chemical mechanical planarization (CMP).
2. Description of the Related Art
In the fabrication of integrated circuits (ICs) and display elements, CMP is used to planarize the surface topography of a substrate for subsequent deposition processes. During CMP, the surface of the substrate to be planarized is brought into contact with the surface of a polishing pad, and the substrate and the polishing pad are rotated and translated relative to each other with a polishing slurry supplied to polish a substrate. After the CMP process is performed for a certain period of time, the polishing surface of the polishing pad becomes glazed due to accumulation of slurry by-products and/or material removed from the substrate and/or the polishing pad. Glazing reduces pad asperity, provides less localized pressure, thus reducing the polishing rate. In addition, glazing may cause the polishing pad to lose some of its capacity to hold the slurry, further reducing the polishing rate.
Typically, the properties of the glazed polishing pad can be restored by a process of conditioning with a pad conditioner. The pad conditioner is used to remove the unwanted accumulations on the polishing pad and regenerate the surface of the polishing pad to a desirable asperity. Typical pad conditioners include an abrasive head generally embedded with diamond abrasives which can be rubbed against the pad surface of the glazed polishing pad to retexture the pad. The abrasive head embedded with diamond abrasives has the advantage of maintaining the removal rate for the polishing pad. However the diamond abrasives may be too aggressive for conditioning the polishing pad and thus shorten the pad life, especially for a soft polishing pad. Hence, it is desirable to have a pad conditioner with proper abrasives for alleviating aggression on the polishing pad, especially on the soft polishing pad. Furthermore, diamond alone can not remove accumulations inside pad grooving, which is usually much deeper than the height of the diamond abrasive.
In addition to the abrasive head of the pad conditioner, a brush can be used to brush off the loosened material and clean up slurry byproduct residues. The brush may be used on a separate conditioning head or attached to the conditioning head in place of the abrasive head during conditioning operations. Although the brush has the advantage of removing slurry by-products, it cannot regenerate pad surface asperity to retain the removal rate throughout the pad life. Hence, it is desirable to have a pad conditioner on which the abrasive head is combined with the brush for simultaneously addressing both removal rate and defect issues, and also saving operation time.